Gov. Nikki Haley waved to the crowd before watching the Republican debate on Jan. 14 in North Charleston, S.C.Credit Andrew Burton/Getty Images

Updated, 6:10 p.m. | CHAPIN, S.C. — Senator Marco Rubio received the endorsement Wednesday of South Carolina’s governor, Nikki R. Haley, a stamp of approval that could prove significant as his campaign tries to break out ahead in the state’s primary on Saturday.

Ms. Haley endorsed Mr. Rubio at an early evening rally in Chapin, S.C., saying, “If we elect Marco Rubio, every day will be a great day in America.” The endorsement puts the backing of one of the Republican Party’s rising stars behind Mr. Rubio, who has cultivated relationships with many of his party’s youngest leaders. Mr. Rubio’s campaign is oriented around a message of letting a new generation of conservatives take the lead. He and Ms. Haley are both 44.

Ms. Haley was persuaded to lend her support as Mr. Rubio tries to rebound from a disappointing fifth-place finish in the New Hampshire primary. His aides increasingly see a strong finish in South Carolina — they predict third place but have said a best-case scenario of second is not impossible — as the surest and quickest way for him to consolidate the support of Republicans who would never vote for Donald J. Trump or Senator Ted Cruz of Texas, the candidates currently leading most South Carolina polls.

Ms. Haley, who is often mentioned as a possible Republican vice-presidential candidate, delivered her party’s response to President Obama’s State of the Union address last month, and used the opportunity to chastise Mr. Trump’s brand of politics, becoming one of the first establishment Republicans to take him on. And she drew wide acclaim from Republicans and Democrats alike last year when she called on South Carolina to remove the Confederate battle flag from in front of the State House in Columbia following the mass shooting in Charleston last June.

This week, she was coy about an endorsement, telling a local television station that Mr .Trump was “everything a governor doesn’t want in a president.”

Together, Mr. Rubio, the son of Cuban immigrants, and Ms. Haley, the daughter of Sikh immigrants from India, hope to form a powerful contrast to an older generation of Republicans who have long controlled the party.

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